Antioxidant composition and ester lubricating oil containing it



bine engines of the pure that consists essentially of at least one United States Patent 3,341,791 ANTIOXIDANT COMPOSITION AND ESTER LUBRICATING OIL CONTAINING IT John W. Thompson and Thomas G. Davis, Kingsport, Tenn., assignors to Eastman Kodak Company, Rochester, N.Y., a corporation of New Jersey No drawing. Filed Feb. 26, 1964, Ser. No. 347,391

- 25 Claims. (Cl. 25233.6)

This invention relates to synthetic, ester type, lubricating oils and to the problem of protecting them from oxidative degradation, especially at temperatures greater than about 300 F.

Synthetic oils of the ester type have replaced petroleum oils in many lubricant and hydraulic fluid applications Where severe service conditions are encountered. As an example, esters such as bis(2-ethylhexyl)sebacate are used almost universally as lubricating oils in aircraft turjet and prop jet types. However, under such severe service conditions, these esters as a class are very susceptible to oxidative degradation. Consequently, in formulating satisfactory jet engine lube oils from esters and the like, measures must be taken to protect these esters from oxidative degradation under these severe service conditions. One such measure is to incorporate into the oil a compound which has been found to inhibit or suppress oxidative degradation of that oil, that is, to function as an antioxidant in and for said oil.

A number of arylamines have been found to be effective antioxidants for ester type, synthetic, lubricating oils at temperatures up to about 300 F. However, these same arylamines have been found to have substantially reduced antioxidant activity or to be generally ineffective antioxidants for synthetic ester oils at temperatures above about 300 F., for example, 400-550 R, which temperatures are those expected to be encountered in the operation of military and civilian jet engines currently under development.

A problem, therefore, to which this invention provides a solution is how to maintain the effectiveness of these arylamines when they are employed in ester type synthetic lubricating oils at these higher temperatures.

This invention is based upon the discovery that alkali metal salts selected from the group consisting of alkali metal salts of carboxylic acids and alkali metal salts of hydroxy aromatic compounds, at minor concentrations relative to certain arylamine antioxidants, substantially maintain the antioxidant activity of these arylamine antioxidants in ester lube oils at these higher temperatures, and even cause various arylamines to be converted from ineffective to extremely potent antioxidants in ester lube oils at these temperatures.

In summary, this invention, broadly considered, comprises an oil composition particularly useful as a lubricant at temperatures as high as 400-550 F. The oil composition consists essentially of a synthetic ester type lube oil and dissolved therein at a protective concentration a mixture consisting essentially of an arylamine portion arylamine and, as a high temperature activator for the arylamine portion, at least one alkali metal salt selected from the group consisting of alkali metal salts of carboxylic acids and alkali .metal salts of hydroxy aromatic compounds.

The synthetic ester type lube oil portion of the composition of this invention consists essentially of at least one ester which is normally liquid at temperatures of at least -25 C. Such an ester includes diesters of dibasic acids and alcohol, diesters of glycols and monobasic acids, trimethylolpropane and trimethylolethane triesters, pentaerythritol tetraesters and low molecular weight polyesters such as those resulting from the reaction of a glycol and a dibasic acid, and terminated with either a monohydric alcohol or a monobasic acid. Typical, specific, synthetic ester oils are:

2-buty1-2-ethyl-1,3-propanediol dipelargonate 2-ethyl-2-isobutyl-l,3-propanediol diundecanoate Bis Z-ethylhexyl) sebacate Dinonyl-2-ethyl-3-methylglutarate 2,2,4-trimethyl-1,3-pentanediol dlpelargonate Bis (2,2,4-trimethylpentyl) azel ate 2,4-dimethyl-2,4-dipropyl-1,3-cyclobutanediol diundecanoate 2,2,4,4,6,6-hexamethyl-1,3,5-cyclohexanetriol triheptanoate Trimethylolethane tripelargonate Trimethylolpropane triheptanoate Pentaerythritol tetrahexanoate Pentaerythritol tetra( 50/50 octanoate/pelargonate) Pentaerythritol tetra(/25 pelargonate/Z-ethylhexanoate) Polyester of neopentyl With 2-ethylhexanol In addition to at least one synthetic ester, the oil portion of the composition of this invention can also consist essentially of two or more normally liquid esters. In such event, the synthetic ester type lube oil is a blend of ester oils.

The arylamine portion of the lubricating oil composition of this invention functions as an antioxidant for the synthetic ester type lube oil component of the composition. General types of arylamines under the concepts of this invention include, in order of preference: diphenylamines, N phenylnaphthylamines, dinaphthylamines, phenothiazines and phenylenediamines. These arylamines are preferred in the order listed on the bases of the dirtiness and effectiveness involved. For example, while phenothiazine currently is used in most jet lubes, it is generally considered to be a dirty antioxidant, especially at higher temperatures. The phenylenediamines such as N,N'-di-2-naphthylphenylenediamines have been dirty and not of the highest eflfectiveness in our tests. Hence, diphenylamines and N-phenylnaphthylamines are especially preferred under the concepts of this invention. Examples of diphenylamines include: diphenylamine, N-methyldiphenylamine, p-octyldiphenylamine, p,p-dioctyldiphenylamine, and the like. Examples of N-phenylnaphthylamines include N-phenyl-l-naphthylamines, N-phenyl-Z- naphthylamines, N (p-dodecylphenyl)-2-naphthylamine, and the like. Examples of dinaphthylamines include di-lnaphthylamine, di-Z-naphthylamine, and the like. Examples of phenothiazines include phenothiazine, N-ethylphenothiazine, and the like. Examples of phenylenediamines include N,N'-di-p-naphthyl-p-phenylenediamine, N,N-diphenyl-p-phenylenediamine, and the like. For extremely high temperature service, the arylamine prefably has substituents such as alkyl groups and the like to reduce the volatility of the arylamine.

The arylamine portion of the mixture employed in the lubricating oil composition of this invention can include two or more other arylamines. An especially preferred combination of arylamines is N-phenyl-l-naphthylamine and 5-ethyl-l0,IO-diphenylphenazasiline at about a 2:1 weight ratio.

The high temperature activator for the arylamine portion of the lubricating oil composition of this invention consists essentially of at least one alkali metal salt selected from the group consisting of alkali metal salts of carboxylic acids and alkali metal salts of hydroxy aromatic compounds. The alkali metal salts of carboxylic acids and alkali metal salts of hydroxy aromatic compounds include the potassium, sodium, lithium, rubidium and cesium salts of these acids and compounds.

glycol and sebacic acid, terminated Alkali metal salts of carboxylic acids are in general represented by the formula:

i R-doM wherein M is an alkali metal radical and R is a carboxylic acid residue. Types of alkali metal salts of carboxylic acids include: alkali metal salts of monobasic acids of the formula:

R-OM wherein R is a C -C hydrocarbon radical which includes saturated and unsaturated aliphatic radicals (for example, alkali metal salts of acetic acid, stearic acid and the like); dibasic acid salts of the formula:

I Mo-i :R"-dM wherein R is a C -C hydrocarbon radical which includes saturated and unsaturated aliphatic radicals (for example, alkali metal salts of oxalic acid, sebacic acid and the like); alkali metal salts of polybasic acids such as those wherein the carboxylic acid residue is obtained by polymerization of unsaturated fatty acids (for example: alkali metal salts of linoleic acid dimer and alkali metal salts of linoleic acid trimer); alkali metal salts of dibasic acid half esters of the formula:

wherein R is a C C hydrocarbon radical which includes saturated and unsaturated aliphatic radicals (for example, alkali metal salts of monoethyladipate, of the monooctyl ester of linoleic acid trimer, and the like); alkali metal salts of carboxy terminated polyesters of 600-4,000 molecular weight, such as those obtained in the reaction of glycols with dibasic acids in stoichiometric excess; alkali metal salts of imide-amide reaction products; and alkali metal salts of cyclic carboxylic acids such as, for example, naphthenic acids and the like.

Alkali metal salts of imide-amide reaction products are made by cooking at a temperature of 190-220 C. until an acid number generally in a range from about to about 150 and preferably in a range from about 25 to about 75 is obtained a mixture consisting essentially of at least one amino carboxylic acid and at least one C C alkyl or (l -C alkenyl primary amine at a mole ratio of acid to amine in a range from about 1:2 to about 1:4, whereby an imide-amide reaction product consisting essentially of imide-amide compounds is formed, neutralizing the reaction product to at least 90% of its acidity with at least one alkali metal hydroxide and then removing water plus any solvent that may be present. Examples of an amino carboxylic acid are ethylenediamine tetraacetic acid (hereinafter referred to as EDTA), iminodiacetic acid, 1,2- cyclohexanediamine tetraacetic acid, and the like. Preferred amines for the imide-amide reaction products include octylamine, Z-ethylhexylamine, dodecylamine, stearylamine, oleylamine and mixtures thereof including C -C t-alkyl primary amine products such as the one marketed as Primene 81R.

Alkali metal salts of hydroxy aromatic compounds are represented by the formulae:

wherein M is an alkali metal radical, R' is selected from the group consisting of C C alkyl, C C alkoxy, aryl, substituted aryl and halide radicals and n is 1-4. The alkali metal salts in this category can be derived from a wide variety of hydroxy aromatic compounds. Examples of alkali metal salts in this category include p-(C -c alkyl)phenols (for instance, p-nonylphenol, p-dodecylphenol and the like), m-pentadecylphenol, p-methoxyphenol, 2,4-dibutylphenol, p-phenylphenol, o-octylphenol, 4-chloro-6-t-butylphenol and the like. In this connection, the phenoxide type metal salts can be prepared by dissolving in each case a selected alkali metal hydroxide in an ethanol-water mixture, adding a chemically equivalent quantity of the selected phenol, stirring and heating to remove solvent and water. Other types of alkali metal salts of hydroxide aromatic compounds include alkali metal salts of naphthols (for example, alkali metal salts of l-phenylazo-Z-naphthol and the like).

Preferred types of alkali metal salts of this invention and the order of their preference are: alkali metal salts derived from amino carboxylic acids, alkali metal salts of naphthenic acids, alkali metal salts of branched chain aliphatic monocarboxylic acids, alkali metal salts of straight chain aliphatic monocarboxylic acids, alkali metal salts of substituted phenols, alkali metal salts of carboxy terminated polyesters and alkali metal salts of dibasic acid half esters. This order of preference is based for the most part on the solubilities of these alkali metal salts in synthetic ester lubricant oils generally. In other words, the more soluble an alkali metal salt is in the ester oil portion of the composition the higher the order of its preference. Alkali metal salts of the group of carboxylic acids and hydroxy aromatic compounds, incompletely soluble initially at the desired use concentration in the ester oil portion are effective and within the scope of this invention. However, it is preferred that the alkali metal salts initially be completely soluble at the desired use concentration in the ester oil portion.

The alkali metal salt can be added as such alone or in admixture With the arylamine to the ester lube oil portion of the composition, or it can be made in situ in the ester oil portion. In the latter instance, however, it is recommended that any water of formation and solvents, which are present in the composition after formulation of the alkali metal salt, be removed, for example, by distillation.

Concentration of the arylamine portion of the ester oil composition depends on the esters employed in the oil portion and on the degree of high temperature stability desired. However, for most uses, concentration of the arylamine portion is generally in a range from about 0.2 to about 10% by weight of the ester oil portion and preferably in a range from about 0.5 to about 6% by weight of the ester oil portion.

Concentration of the alkali metal salt portion of the lubricating oil composition of this invention depends on the arylamine or arylamines employed in the composition and on the degree of high temperature activation desired. However, for most uses of the lubricating oil of this invention, the concentration of the alkali metal salt is selected to give an equivalent, total, alkali metal concentration in a general range from about 0.001 to about 0.5% by weight of the ester oil portion and preferably in a range from about 0.005 to about 0.5% by Weight of the ester oil portion with the Weight ratio of total equivalent, alkali metal to said arylamine antioxidant portion being in a general range from about 1:30 to about 1:1000.

The lubricating oil composition of this invention is made by admixing the components thereof preferably at 5090 C., although lower and higher temperatures can be employed.

In some embodiments of this invention, it is preferred to admix first the arylamine portion of the composition and the alkali metal salt portion of the composition, thereby forming a stabilizer mixture, and then add the stabilizer mixture to the ester oil portion of the composition. In such embodiments, the concentration of the mixture is in a range from about 0.2 to about 10% by weight of the ester oil portion and preferably in a range from about 0.5 to about 5% by weight of the ester oil portion.

In addition to a new lubricating oil composition, this invention also provides a new antioxidant composition. This composition consists essentially of an arylamine por- .dant composition in such an oil of arylamines involved in these new antioxidant compositions have already been described herein in considerable detail. Also the alkali metal salts of these new antioxidant compositions have been hereinbefore described in considerable detail. In general, the weight ratio of the alkali metal salt portion to the arylamine portion of the antioxidant composition is in a range from about 1:1000

to about 1:30.

The new antioxidant composition of this invention is made by admixing the components preferably at 50- 90 C., although higher and lower tempeartures can be employed.

This new antioxidant composition is particularly useful in synthetic ester oils employed as high temperature lubricants, such as those previously described herein, The recommended concentration range of this new antioxiis generally from about by weight of the ester oil and pref- 0.5 to about 5% by weight of the 0.2 to about erably from about oil.

This invention is further illustrated by the following examples of various aspects of this invention, including specific embodiments thereof. This invention is not limited to these specific embodiments unless otherwise indicated.

Examples 1-17 These examples illustrate specific embodiments of an ester lube oil composition of this invention, which are based on alkali metal salts of carboxylic acids as the high temperature activators for the arylamine antioxidants employed therein.

In each of the specific embodiments of these exam- 6 ples, the ester lube oil portion of the composition is 2-butyl-2-ethyl1,3-propanediol dipelargonate. The arylamine antioxidant is a mixture consisting essentially of N-phenyl-l-napthylamine at a concentration of 1% by Weight based on the ester and 5-ethyl-10,10-diphenylphenazasiline at a concentration of 1% by weight based on the ester. The composition (components, concentration, and equivalent alkali metal concentration) of thealkali metal salt portion of each specific embodiment of these examples is given in the following Table I. These specific embodiments are made by admixing the components at -90 C.

Table I also sets forth typical data actually obtained in testing for oxidative stability at temperatures over 300 F. samples of these specific embodiments, of the ester oil alone and of the ester oil with one or the other of the arylamine antioxidant and alkali metal salt portions present. The test employed in obtaining these data is referred to herein as the 425 F, AF Oxidation Test. It is described in a paper entitled Materials for High Temperature Jet Engine Lubricants by H. B. Adams in WADC Technical Report 59-244 (US. Air Force, 1959). In this test a 250 milliliter sample of the lube oil composition is heated at 425 F. in a Pyrex test tube while 96 liters of air per hour are blown through the oil composition. Freshly polished 1 inch x 1 inch x inch coupons of steel, copper, aluminum, titanium and silver, assembled as in Method 5308.4 of Federal Test Method Standard 791, are immersed in the oil. The tube is capped with a Pyrex fitting which allows volatile products to escape. The composition is heated in 20 hour cycles and at the end of each cycle the tube is cooled, a 10 milliliter oil sample is withdrawn for analysis and the oil lost by evaporation is replaced. Ordinarily, the test is continued for six cycles or 120 hours. The 10 milliliter speci mens are analyzed for viscosity in centistokes at 100 F. (ASTM Method D445) and for acid number (ASTM Method D974). An increase in viscosity and an increase in acid number denote oxidation with the extent of oxidation being proportional to the extent of the increase in viscosity and in acid number.

TAB LE I Alkali Metal Salt Portion 425 F. AF Oxidation Test Results Example No. Equivalent Concentration, alkali metal Viscosity in Oomponent(s) percent by wt. concentration, Oxidation centistokes Acid N o.

01' ester oil percent by wt. time in hours at 100 F.

portion of ester oil portion 1 Sodium stearate 0. 064 0.005N a- 21. 5 1. 6 2 I Sodium stem-ate 0. 27 0.02Na 120 18. 4 0. 6 3; Sodium propionate 0. 04 0.01-N a 120 18. 3 0. 6 4 Sodium pel 0. 08 0.01-N a 120 19.8 1. 3 Sodium oleate 0. 13 0.01-Na 120 19. 2 1. 1 Potassium stearate 0. 17 0.02K 120 17. 9 0. l Lithium stearate 0. 84 0.02-Li 120 22. 2 1. 3 Monopotassium salt of dimer of oleic acid 0. 16 0.01-K 100 19. 1 1. 7 Potassium monoethyl adipate 0. 067 0.01-K 100 18. 8 1. 1 10 Potassium salt of imideamide reaction product of 0.25 0.01-K 17. 4 0.4

Acid'No. 49 and derived from EDTA and 0 143 t-alkyl primary amine mixture reacted on 1:3 mole ratio basis.

11 Potassium salt of imide-amide reaction product of 2. 50 0.1K 120 17.2 0. 2

Acid No. 49 and derived from EDTA and 019-015 kyl primary amine mixture reacted on 1 3 mole ratio basis.

12 Sodium salt of imide-amide reaction product of 0. 25 0.01-Na 100 18. 9 1. 1

Acid N o. 49 and derived from EDTA and C 2- C t-alkyi primary amine mixture reacted on 1 3 mole ratio basis.

TABLE IConi:inued Alkali Metal Salt Portion F. AF Oxidation Test Results Example No. Equivalent Concentration, alkali metal Viscosity in Component(s) percent by wt. concentration, Oxidation centistokes Acid No.

of ester oil percent by wt. time in hours at 100 F.

portion of ester oil portion 13 Cesium salt of imideamide reaction product of 0.074 0.01-Cs 40 19. 4 2. 5

Acid No. 49 and derived from EDTA and 017-015 t-alkyl primary amine mixture reacted on 1 3 mole ratio basis. 14 Potassium salt of imide-amide reaction product of 0. 0.01--K 100 17. 5 0. 5

Acid No. 141 and derived from EDTA and C1:- C t-alkyl primary amine mixture reacted on 1 2 mole ratio basis. 15 Potassium salt of imide-amide reaction product of 0. 14 0.01K 100 17. 8 0.9

Acid No. 100 and derived from EDTA and 2- ethylhexylamine reacted on 1 2 mole ratio basis. 16 Potassium salt of imide-amide reaction product of 0. 32 0.01-K 100 17. 6 17.7

Acid No. 42 and derived from imino diacetie acid and Crz-Crs t-alkyl primary amine mixture reacted on 1 2 mole ratio basis. 17 Potassium salt of imide-amide reaction product of 0. 174 0.01-K 100 17.2 0.4

Acid No. 79, and derived from 1, Z-cyclohexanediamine tetraacetic acid and C C| t-alkyl primary amine mixture reacted on 1:3 mole ratio basis. Ester oil without any arylarnine antioxidants and without any alkali metal salts- 0 14. 32 0. 0 229 18. 7

Ester oils with the aiylamine antioxidants and without any alkali metal salts 2g 14. 88 0. 02

Ester oil without any arylamine antioxidants but with potassium salt of imide- 0 14. 49 0.04 amide reaction product of Acid No. 49 and derived from EDTA and C r-C 5 t- 20 80.9 9.5 alkyl primary amine mixture on 1:3 mole basis, the salt being at a concentration of 0.25% by weight of ester oil, representing 0.01% by weight of K.

Thus, there are p compositions having a to oxidation degradation a rovided specific ester oil lubricant higher degree of protection relative t high temperatures. Compariessentially of N-phenyl-l tion of 1% by Weight base nate. The arylamine antioxidant is a mixture consisting -naphthylamine at a concentrad on the ester oil and S-ethylson of the test data in Table I shows that a variety of alkali metal salts of carboxylic acids are effective high temperature activators for the arylamine antioxidants employed.

Examples 18-22 These examples illustrate specific embodiments of the composition of this invention,

metal salts of hydroxy aromatic compounds.

The ester oil employe bodiments is 2-butyl-2-ethyl-1,3

which are based on alkali d in each of these specific em- -propanediol dipelargocomponents at -90 C.

These specific embodiments are made by admixin g the Also in Table II are typical data actually obtained in testing for oxidative stability at temperatures over 300 TABLE II Alkali Metal Salt Portion 425 F. AF Oxidation Test Results Equivalent Example No. Concentration, alkali metal Viscosity in Component (5) percent by wt. concentration, Oxidation centistokes Acid No.

of ester oil percent by wt. time in hours at F.

portion of ester oil portion 18 Potassium (p-nonyl-phenoxide) 0. 065 0.01-K 16.8 o. 6 19 Potassium (p-methoxy-phenoxide) 0.65 0.1-K 120 18. 7 0, 0 20 Sodium (p-nonyl-phenoxide) 0.11 0.01-Na 120 19.1 1. 2 21 Potassium (2phenyl-4-chlorophenoxide) 0. 63 0.01K 120 18. 3 0, 5 22 Potassium (p-methoxy-phenoxide) 0. 038 0.01K 21. 8 3, 0

Ester oil without any arylamine antioxidants and without any alkali metal salts- 0 14. 32 0.03

Ester oil with the arylamine antioxidants but without any alkali metal salts O 14. 88 0.03

Ester oil without any arylamine antioxidants but with potassium (p-nonyl- 0 14. 40 0.03 phenoxide) at a concentration of 0.065% by weight of ester oil, representing 0.01% 20 66. 2 9. 7 by weight based on the oil oi K.

Examples 23-34 These examples illustrate specific embodiments of the ester oil composition of this invention, involving various arylamine antioxidants.

The ester oil employed in each of the specific embodiments is 2-butyl-2-ethyl-1,3-propanediol ,dipelargonate. The composition (components and concentration) of the arylamine antioxidant portion and of the alkali metal salt portion of each of these specific embodiments are set forth in the following Table III.

These specific embodiments are made by admixing the components thereof at 5090 C.

Table III also includes typical data actually obtained in testing for oxidative stability at temperatures over 300- F. samples of these specific embodiments and of the ester oil containing only the specific arylamine antioxidants. The test employed in obtaining the data is the 425 F. AF Oxidation Test. I i l i i TABLE III Arylamine Antioxidant Portion Alkali Metal Salt Portion 425 F. AF O id ti T t Equivalent Con ntra- C Joneentraalkali metal Oxlda- Viscosity Example tion in pertron in perconcentration in centi- Acid No. Component(s) cent by wt. Compnent(s) cent by Wt. tron 111 pertime in stokes at No. of ester oil of ester 01] cent by wt. hours 100 F.

portion portion of ester oil portion N-phenyl-l-naphthyl- 1 None 0 14, 8 0 3 amine. 20 30. 2 6. 2 -ethyl-10,10,-diphenyl- 1 40 49. 4 7. 5

phenazasiline.

23 N -Dhenyl-1-naphthyl- 1 Potassium salt of imide-amide 0.50 0.02K 120 16. 2 0.20

amine. reaction product of Acld N o. 5-ethyll0,10- diphenyl- 1 49 and derived from ED TA phenazasilme. and Cir-C t-alkyl primary amine mixture reacted on 1:3 mole ratio basis.

v24 N -phenyl-1-naphthyl- 0. 5 Potassium salt of imide-amide 0. 25 0.01K 120 16. 2 0. 00

amine. reaction product of Acid N o. 5-ethyl-10,10-diphenyl- 0.5 49 and derived from E D TA phenazasiline. and O e-C t-alkyl primary amine mixture rcac ted on 1:3 mole ratio basis.

25.; N -phe'nyl-1-naphthyl- 1. 5 Potassium salt of imide-amide 0.25 0.01K. 140 16. 8 0. amino. reaction product of Acid N o. 5-ethyl-10,10-diphenyl- 0.5 49 and derived from EDTA phenazasiline. and Cir-C15 t-alkyl primary amine mixture reacted on 1:3 mole ratio basis.

N-phen -1-naphthyl 2 N 10 63A 9.9 amine.

26 N -phenyl-1-naphthyl- 2 Potassium salt of imide-amide 0.25 0.01K- 140 17. 41 1. 10

' amine. reaction product of Acid N 0.

49 and derived from EDTA and 012-015 t-alkyl primary amine mixture reacted on 1:3 moleratio basis.

27. N-phenyl-l-naphthyli 2 Potassium (p-nonyl-phenoxide) 0 065 0.0lK. 140 17. 0.65

* amine.

fi ethyl-l'o dtidiphenyl- 2 None 20 190 20. 7

phenazasiline.

28 5-ethyl-10,10-diphenyl- 2 Potassium (p-nonyl-phenoxide) O 065 0.01K 40 29 4. 2

. phenazasiline.

N ethylphenothiazine 1 None 40 37. 7 12. 8 P,P'-diocty1diphenyl- 1 amine.

29 N-ethylphenothiazine 1 Sodium stearate 0. 27 0.02Na 20 36.}! 3. 4

P,P-dioctyldiphenyl- 1 amine.

N -phenyl1-naphtl1yl- 1 None 20 36. 8 8, 4'

amine. P,P-dioctyldiphenyl- 1 amino.

30 N-phenyl-l-naphthyl- 1 Sodium stearate 0. 27 0.02Na 22. 8 1. 85

am e. P,P--dioetyldiphenyl- 1 amine.

31 N-phenyl-l-naphthylamine 1 Potassium salt of imide-arnide 0.25 0.01-K 26. 6 1. 60

P,P-dioetyldipheuylareaction product of Aeld N o. mine. 49 and derived [tom EDTA and Cl2-Cl5 t-alkyl primary amine mixture reacted on 1:3 mole ratio basis.

TABLE III- Continued Arylamine Antioxidant Portion Alkali Metal Salt Portion 425 F. AF Oxidation Test Equivalent Concentra- Concentraalkali metal Oxida- Viscosity Example tion in pertion in perconcentration in centi- Acid N 0. Component cent by wt. Component (s) cent by wt. tion in pertime in stokes at No.

of ester oil of ester oil cent by wt. hours 100 F.

portion portion of ester oil portion N-phenyi-l-naphthylar 1 None 42. 6 10. 7

mine. Diphenylarnine 1 32 N-pheny1l-naphthy1- 1 Potassium salt of imide-amide 0. 50 0.02-K 140 16. 3 0.00

amino. 1 reaction product of Acid No. Diphenylamine 49 and derived from EDTA and 012-015 t-alkyl primary amine mixture reacted on 1:3 mole ratio basis. N,N-di(B-naphthy1)-p- 2 None 40 40.1 9.0

phenylenediamine. 33 N ,N'-di(6-naphthyl)-p- 2 Potassium salt of imide-amide 0. 0.01-K 80 20. 8 2.18

phenylenediamine. reaction product of Acid No.

49 and derived from EDTA and 012-015 t-alkyl primary amine mixture reacted on 1:3 mole ratio basis. Phenothiazine 1 None 40 26. 9 6. 4 34 Phenothiazine 1 Potassium salt of imide-amide 0. 25 0.0l--K 40 18. 7 4. 3

reaction product of Acid No. 49 and derived from EDTA and Cu-Crs t-alkyl primary amine mixture reacted on 1:3 mole ratio basis.

Thus, there are provided more, specific ester oil compositions useful as high temperature lubricants.

These examples illustrate specific ester oil lubricant of this invention, involve other esters which are oils at 2025 Examples 35-41 are used as base stocks for lubricants.

The esters called for by the these specific embodiments are i The arylamine antioxidant portion of each of of Examples 35 and 36 consists -naphthylamine at a concentraester oil portion of these Table IV. the specific embodiments essentially of N-phenyl-l tion of 0.5% by weight of the specific embodiments and 5-ethyl-10,10- siline at a concentra oil portion of these s embodiments of the which embodiments formulations of each of ndicated in the following tion of 0.5 by weight of the ester pecific embodiments. The arylamine C. and which diphenylphenaza- TABLE IV These specifi blending together the compon Table IV also contains typic in running the 425 these specific embodiments an oils containing only the correspon oxidant portions just described.

antioxidant portion of each of the of Examples 37-41 consists essen naphthylamine at a co the ester oil portion 0 entrations and equiv the alkali metal salt portion of each ncentration of 1% f each of these specific embodiments and S-ethyl-lO,IO-diphenylphenazasiline at a concentration of 1% by weight of the es each of these specific embodiments. (components, conc concentrations) of embodiment is presented in Table IV.

F. AF Oxidation Te specific embodiments tially of N-phenyl-lby Weight of ter oil portion of The composition alent alkali metal 0 embodiments likewise are made by ents at -90 C.

a1 data actually obtained st on samples of d on the indicated ester ding arylamine anti- Alkali Metal Salt Portion 425 F. AF Oxidation Test Example Ester Oil Portion Concentra- Equivalent Viscosity N tion in peralkali metal Oxidation in centi- Acid Component(s) cent by wt. concentration in time in stokes at No.

of ester oil percent by wt. of hours F.

portion ester oil portion 2-ethyl-2-isobutyl-1,3-propanediol N01 0 13. 83 0.02 dipelargonate. 20 47. 4 10. 60 35 2ethyl-2-isobutyl-1,3-propanediol Sodium stearate 0.13 0.01Na 17. 9 0.76

dipelargonate. Bis(2,2,4-trimethylpentyl)azelate. Non 0 13.82 0. 04

36 Bis(2,2,4-trimethylpentyl)azelate. Potassium(pnonylphenoxide). 0.065 0.01-K 17. 2 0. 59 Trimethylolpropanetriheptanoate. Non 0 15. 26 0. 04 2O 26. 9 4.19

37 Trimethylolpropanetriheptanoate. Potassium salt of imide-amide 0.25 0.01-K 60 16. 4 0.00

reaction product of Acid No. 49 and derived from EDTA and 012-015 t-alkyl primary amine mixture reacted on 1:3 mole ratio basis. Pcntaerythritoltetrahexann None 0 28. 26 0. 19

Thus, there are provided a number of embodiments of the ester oil lubricant composition of this invention, which are based on various ester oils.

Examples 42-53 These examples illustrate more, specific embodiments of the ester oil compositions of this invention.

The ester oils in the formulations of each of these specific embodiments are identified in the following Table V. The composition of the arylamine antioxidant portion and the composition of the alkali metal salt portion are also comp TABLE IVContinued Alkali Metal Salt Portion 425 F. AF Oxidation Test Example Ester Oil Portion Concentra- Equivalent Viscosity No. tion in peralkali metal Oxidation in centi- Acid Component(s) cent by wt. concentration in time in stokes at No.

of ester oil percent by wt. of hours 100 F.

portion ester oil portion 38 Pentaerythritoltetrahexanoate Potassium salt of imide-amide 0. 25 0.01-K 120 35. 4 0.31

reaction product of Acid N o. 49 and derived from EDTA and Crz-Cus t-alkyl primary amine mixture reacted on 1:3 mole ratio basis.

2,2,4-trimethyl-1,3-pentanediol None t 12. 31 0. 07 dipelargonate. 2O 26. 8 7. 39 '2,2,4-trimethyl-1,8-pentanediol Potassium salt of imide-amide 0. 25 0.01K 120 17. 5 0.45

dipelargonate. reaction product of Acid N o. 49

and derived from EDTA and Cir-C t-alkyl primary amine mixture reacted on 1:3 mole ratio basis.

Bis(2ethylhexyl) sebacate None 0 13. 0 0. 05

60 41. 0 22. 7 40 Bis (2-ethylhexyl) sebacate Potassium salt of imide-amide 0. 0.01-K 120 16. 9

reaction product of Acid No. 49 and derived from EDTA and C 12-0 5 t-alkyl primary amine mixture reacted on 1:3 mole ratio basis.

Polyester oi neopentyl glycol and None 0 1, 585 1. 06 sebaeic acid, and terminated 7, 652 4. 80 with 2-ethylhexanol, all reacted on a 2: 1:2 mole ratio basis.

41 Polyester of neopentyl glycol and Potassium salt of imlde-am de 0. 25 0.01-K 40 4, 469 2. 64

sebacic acid, and terminated reaction product of Acid N o. 49 with Z-ethylhexanol, all reacted and derived Irom EDTA and on a 2:122 mole ratio basis. Cir-01s t-alkyl primary amine mixture reacted on 1:3 mole ratio basis.

These specific embodiments are made by admixing the testing for oxidative stability samples of these specific embodiments. The test employed is referred to herein as the 500 F. oxidation test. In this test 36 liters of air per hour are passed through a 25 milliliter sample of the oil composition under test, which sample contains a 1 inch length of diameter, freshly polished, iron wire. While the air is passed through the sample, the temperature of See footnotes at end of table.

set forth in Table V. the sample is established and maintained at about 500 F.

' TABLE v Ester Oil Portion Arlyamine Antioxidant Portion Alkali Metal Salt Portion 500 F. Oxidation Test Results Con- 0011- Equiv- Oxida- Viscos- N0. cencenalent tion ity in Acid Components Components tra- Components traalkali time centi- No.-

tion 1 tion 1 metal in stokes at concenhours .100 F. tration 1 Pentaerythritol tetra None None 0 34. 01 0.00 (/50 octanoate/ 20 pelargonate). p a v Pentaerythritol tetra N-(p-I I LzElIeeylphenyD-Z- 3. 56 None 0 38. 01 0. 00

50 50 octanoate/ nap y amine. 'pclirgonate). 5-Ethyl-10,10-diphenyl- 1 20 9, 000 16. 2 phenazasiline. pp 42 Pentaerythritol tetra N-(p-dodecylphenyD-Z- 3.56 Potassium salt of imide- 2.5 0.01K 69.5 0.13

' (50/50 octanoate/ naphthylamine. amide reaction product pelargonate). 5-Ethyl10,10-diphenyl- 1 of Acid N o. 49 and dephenazasiline. rived from EDTA and O a-C t-alkyl primary amine mixture reacted on 1:3 mole ratio basis.

Pentae thritol tetra N-phenyld-naphthylamine- 2 Potassium salt of imide- 2. 5 0.02K 0 351 0 0. 04 I 43 (50/5gctanoate/ 5 etll1iy1-10,101diphenyl- 1 aznidegeNactigi prgdiuct 20 63.1 1.2

enazasi inc. 0 c1 0. an epelargonat) p rived from EDTA and Crz-Cm talkyl primary amine mixture reacted on 1:3 mole ratio basis.

TABLE V-'Con tin'ued Ester Oil Portion Arlyamine Antioxidant Portion Alkali Metal Salt Portion 500 F. Oxidation Test Results Ex. Con- Con- Equiv- Oxida- Viscos- No. cen cenalent tion ity in Acid Components Components tra- Components traalkali time centi- No.

tion 1 tion 1 metal in stokes at concenhours 100 F. tration 1 44 Pentaerythritol tetra N-phenyl-l-naphthylarnine 2 Potassium (p-nonyl 0.13 0.02K 35. 0 0.01 (50/50 octanoate/ -ethyl-10,10-diphenyl- 1 phenoxide). 20 54.1 0. 70 pelargonate). plienazasiline.

45 Pentaerythritol tetra -Octyldiphenylamine 2. 60 Potassium salt 01 imidc- 0.5 0.02K 20 54. 1 0.73

(50/50 octanoate/pel- 5ethyl-10,10-diphenyl- 1 amide reaction product; argonate). phenazasiline. of Acid No. 49 and de rived from EDTA and 0 -0 5 t-alkyl primary amine mixture reacted on 1:3 mole ratio basis.

46. Pentaerythritol tetra N-(p-dodecylpheny1)-1- 3. 56 Potassium salt of imide- 0. 5 0.02-K.- 20 50. 71 0.85

(50/50 octanoate/pelnaphthylarnine. amide reaction product argonate). 5-ethyl-10,l0-diphenyl- 1 of Acid No. 49 and dephenazasiline. rived from EDTA and C Cl t-alkyl primary amine mixture reacted on 1:3 mole ratio basis.

47 Pentaerythritol tetra Di-2-naphthylamine 2. 47 Potassium salt of imide- 0.5 0.02-K-.- 20 45. 1 0. 28

(50/50 octanoatelpel- 5-ethyl-10,10-diphenyl- 1 amide reaction product argonate). phenazasiline. of Acid No. 49 and de rived from EDTA and C12-C t alkyl primary amine mixture reacted on 1:3 mole ratio basis.

48 Pentaerythritolitetra N-butyldiphenylarnine 2 Potassium salt of imide 0. 5 002-15.. 61.0 0. (50/50 octanoate/pel- 5-ethyl-10,10-d1phenyl- 1 amide reaction product 95 argonate). phenazasiline. of Acid No. 49 and derived from EDTA and Org-C15 t-alkyl primary amine mixture reacted on 1:3 mole ratio basis.

49 Pentaerythritol tetra Dodecyl ester of 2anilino- 3. 48 Potassium salt of imide- 0.5 0.02-K- 20 63. 7 0. (50/50 oetanoate/pelbenzoic acid. amide reaction! product 85 argonate). 5-ethyl-l0,10-diphenyl- 1 oi Acid No. 49 and de phenazasiline. rived from EDTA and ir-C15 talkyl primary amine mixture reacted on 113 mole ratio basis.

50 Pcntaerythritol tetra N-(p-dodecylphenyD-Z- 3. 56 Potassium salt of imide- 5 0.20-K 0 45. 16 0.

(50/50 octanoate/pelnaphthylam lne. amide reaction product 37 argonate). 5-ethyl-10,l0 diphenyl- 1 of Acid No. 49 and de- 100 81.8 0.

phenazasiline. rived from EDTA and 01 -0 t-alkyl primary amine mixture reacted on 1:3 mole ratio basis. N

51.- Pentaerythritol tetra N-(p-dodecylphenyD-2- 3. 56 Potassium salt of imide- 2. 5 0.10K 0 40. 20 0.- (/50 octanoate/ naphthylamine. amide reaction product 43 pclargonate). of Acid No. 49 and de- 60 62.6 0.

rived from EDTA and 71 012-015 t-alkyl primary amine mixture reacted on 1:3 mole ratio basis.

52. 2 butyl-2-ethyl-1,3- N-(p-dodecylphenyl)-2- 3. 56 Potassium salt of imidc- 0. 50 0.02K 0 27. 66 0.

propanediol dilaurate. naphthylamine. a ide rea tion roduct 05 5-ethyl-l0,10'diphenyl- 1 of Acid No. 49 and de- 20 35. 3 l. phenazasiline. rived from EDTA and 2 612-015 t'alkyl primary amine mixture reacted on 1:3 mole ratio basis.

53 2,4-dimethyl-2,4,dipro- N-(p-dodecylphenyD-2- 3. 56 Potassium salt of imide- 2. 5 0.10K-. 0 39. 1O 0.-

py y u ep t y m amide reaction product 41 diol diundecanoate. 5ethyl-l0,10- diphenyl- 1 of Acid No. 49 and de- 20 52. 9 l.

phenazasiline. rived from EDTA and 2 CIT-C15 t-alkyl primary amine mixture reacted on 123 mole ratio basis.

1 In percent by weight of ester oil portion. 2 Thick grease.

Examples 54-60 These examples illustrate still more embodiments of the ester oil composition of this invention.

The ester oil portion in each of these specific embodiments consists essentially of 2-butyl-2-ethyl-1,3-propanediol dipelargonate. The arylamine antioxidant portion in each of these specific. embodiments consists essentially of N-phenyl-l-naphthylamine at a concentration of 1% of the weight of the ester oil portion and 5-ethyl-10,10-diphenylphenazasiline at a concentration of 1% of the weight of the ester oil portion. The composition of the alkali metal salt portion is given in the following Table VI.

These specific embodiments are made by thoroughly 5 blending together th Samples of these speci e components at 50-90 C.

fic embodiments as well as of the ester oil portion alone, with an arylamine antioxidant portion only and with an alkali metal salt portion only were actually prepared and tested for oxidative stability 75 nium coupon. The test res RAF ults are summarized in Table VI.

TABLE VI Alkali Metal Salt Portion Modified 425 F. AF Oxidation Test Results Example Concentration Equivalent 4 No. of salt in peralkali metal Oxidation Viscosity Acid Components cent by wt. of concentration time in in centi- No.

ester oil in percent by hours stokes at portion wt. of ester oil 100 F.

portion 7 1a 45 0. 02 54 Potassium'selt ot l-naphthol 0. 046 0.01-K 120 15. 97 0. 38 55 Potassium salt of l-hydroxyanthraquinone 0. 067 0.01K 0 14. 74 0. 03 b 40 17. 7g 2. so 56 Potassium salt of l-phenylazoZ-naphthol 0. 073 0.01K 0 15. 44 0. 01 I 12c 18. ca 9.70 57 Potassium salt of neotridecanoic acid 0. 065 0.01-K 0 14. 90' 0. 02 120 17. 62 0. 72 58 Sodium salt of neotridecanoic acid- 0. 061 0.006Na. 14. 76 0. 03 120 19. 34 1. 54 59 Dipotassiumsalt of acid terminated polyester of pimelic acid and 0. 26 0.01-K 0 14. 36 '0. 01 1,4-cyclohexanedimethanol reacted on a 1:1 mole ratio basis. 1 22. 67 2. 00 60 Potassium salt of naphthenic acid product of average molecular 0. 088 0.01-K 0 15. 05 0. 01 weight of 310 and Acid No. of 169. (Sunaptic Acid A). I 120 18. 0. 88

1 W Ester all without any arylamine antioxidants but with potassium salt of naphthenic acid product 0 13. 89 0.02 01 average molecular weight of 310 and Acid N o. of 169 (Sunaptic Acid A), the salt being present at 120 71. 77 12. '56 a concentration of 0.088% by weight of the ester oil and equivalent to K concentration of 0.01% of the weight of the ester oil.

Ester oil without any arylamine antioxidants and without any alkali metal salts 20 2%4. 32 1g? 0 9 c. Ester oil with arylamine antioxidants but without any alkali metal salts 23 39 8. 3g 40 az' 111 a ..4'."Ri? 51: 5 These examples illustrate more'embodiments of the ester oil composition of this invention.

-. -.b y -2:et 1.1. :r paned d p l rgcna e...is-.the-.4 o

ster Oll portion of these embodiments. The compositions and concentrations of the arylamine antioxidant portion and the alkali metal salt portion of these embodiments are 7 given'in the following Table VIIQ The octylated styrenated diphenylamine product called for by some of the formulations involved in these specific embodiments is a normally liquid, oily product consist r essentially of Pipfo lY d p enylaniine, "pa"- yldiphenylamihe, '(4)' "p-niono-t-octyldiphnylamine and (5) p-mono-a-phenethyldiphenylamine in the ratio of 70% by weight of (l), (2), and (3) to 30-50% by weight of (4) and (5), said product resulting from the reaction di-a-phenethyldiphenylamine, (3) p-t-octyl-p'-u-phenethof- -1.3 to -2.0 chemical-equivalents of a hydrocarbonmixture containing diisobutylene and styrene in the ratio of 55 2-5 parts by weight of diisobutylene to 1 part by weight of styrene, with one chemical equivalent ofdiphenylamine. with. the aid of a Friedel-Crafts condensation catalyst such as aluminum chloride, at a temperature of ISO-200 C. This product and its synthesis is described in the [1.5. patent, No; 2,530,769, "to Hollis. It is marketd a si Goodrite Staylite.

The octylated diphenylamirie product called for in these embodiments is a "mixture consisting essentially 'of"di-' phenylamines substituted by octyl groups. The mixture is derived from diphenylarnine; The product is available commercially as Vanlube 60.

- The specific embodiments involvedin these examples TABLE VII Arylamine Antioxidant Portion Alkali Metal Salt Portion Modified 425153. i:AF Oxidation Example Concentra- Concentra- Equivalent Oxida- Viscosity No. tion in pertion in peralkali metal tion time in eenti- Acid Component(s) cent by wt. Component(s) cent by wt. concentrain hours stokes at N o.

of ester oil of ester oil tion in per- F. portion portion cent by wt.

of ester oil portion Octylated styrenated 1 None 0 14.24 0.03 diphenyiamineproduct. 20 81. 3 9. 66- Octylated styrenated 1 Potassium salt of imide-amide 0.5 0 02K 0 14.65 0.03 diphenylamine product. reaction rodnct of Acid No. 18.71 0.39 v 49 and erived from EDTA and Cir-01s t-alkyl grimary amine mixture reacte on 1:3 mole ratio basis.

TABLE VII-Continued Arylamine Antioxidant Portion Alkali Metal Salt Portion Modified 425111 9F Oxidation Example Concentra- Concentra- Equivalent Oxida- Viscosity No. tion in pertion in peralkali metal tion time in centi- Acid Component(s) cent by wt. Component(s) cent by wt. concentrain hours stokes at lie.

of ester oil of ester oil tion in per- 100 F.

portion portion cent by wt.

of ester oil portion 62 Octylated styrenated 2 Potassium salt of naphthenic 0. 18 0. 02K 16. 43 0.05

diphenylamine product. acid product of average molec- 80 21. 60 0; 77'

ular weight of 310 and Acid No. of 169. (Sunaptic Acid A).

Octylated diphenylamine 1 None 0 14. 30 0. 01 product. 20 129. 9 13. 44

63 Octylated diphenylamine 1 Potassium salt of imide-amide 0.5 0.02K 0 14.35 0.02 product. reaction product of Acid No. 140 18. 58 0.29

49 and derived from ED'I A and C12-'C15 t-alkyl primary amine mixture reacted on 1:3

mole ratio basis.

64 p,p-Dioctyldiphenyl- 2 Potassium salt of imide-amide 0.5 0. 02K 0 15. 30 0. 03

amine. reaction product of Acid No. 80- 21.88 0; 52

49- and derived from EDTA and 0 1-015 t-alkyl primary amine mixture reacted on 1:3 mole ratio basis. 65- N-(p-dodejcylphenyD- 3. 6 Potassium salt of imide-amide 0.25 0. 01K O 16.12 0.01 2-naphthylamine. reaction product of Acid No. 80 24.83 0.30

49 and derived from EDTA and Cit-C t-alkyl rimary amine mixture reacte on 1:3 mole ratio basis.

Octylated styrenated 0. 4 None. 0 13.89 0. 01 diphenylamine prod- 46. 88 0.35 uct.

66 Octylated styrenated 0.4 Potassium salt of imi'de-amide 0. 0. 01'K 0 14. 55 0. 03 diphenylamine prodreaction product of Acid No. 80 13, 1, 11 uct. 49 and derived from EDTA and O -C t-alkyl primary amine mixture reacted on 1:3 mole ratio basis. N-phenyl-i-naphthyl- 1 None-- 0 14. 88 0.03

amine. 59. 4 7. 5 5-ethyl-10,10-diphenylphenazasiiine.

67 N phenyl-l-napbthyl- 1 Sodium stearate 0.064 0.005-Na... 0 14. 92 0.03

amine. 120 21. 5 1. 6

5-ethyl-10,10-diphenyl- 1 phenazasiline.

68 N-phenyl-l-naphthyi- 1 Potassium salt 0! naphthenio 5.6 0. 63K- 0 17. 0.06 amine. acid product of average 100 17. 83 0. 28

5-ethyl-10,10-diphenyl- 1 molecular weight of 310 and phenazasiline. Acid No. of 169. (Sunaptic Acid A). Nph enyl'-1-naphthyl- 5 None 0 15. 44 0. 01 amine. 120 34. 58 3.49

69 N-phenyl-l-naphthyl- 5 Potassium salt of naphthenic 1. 0 0.11K 0 16. 32 0. 05

' amine. acid product of average V 120 28.80 0. 61

molecular weight of 310 and Acid No; of 169. (Sunaptic Acid A).

These examples illustrate additional specific embodiments of the ester oil composition of this invention.

The ester oil portion, the arylamine antioxidant portion and the alkali metal salt portion of these specific embodiments are given in the following Table VIII. The octylated styrenated diphenylamine product is described in conjunc- Exampl'es 70-76 tion with Examples-.6l69.

These specific embodiments are made by thoroughly mixing together at -90 C. the components thereof.

Table VIII also contains the results obtained in actually that instead of a copper coupon afstainless'steel coupon is employed and the temperature of the samplejis established and maintained at 500 F. This test is hereinafter referred to as the 500 F. AF Oxidation Test.

TABLE VIII Ester Oil Portion Arlyamine Antioxidant Portion Alkali Metal Salt Portion 500 F. AF Oxidation Test Results Ex. Con- Con- Equiv- Oxida- Viscos- No, eencenalent tion 7 ity in Acid Components Components tra- Components traalkali time centi- N 0. tion i tion 1 metal in stokes at concenhours 100 F tratlon Pentaerythritol tetra- None N one o 0, 04 (75/25 pelargonate/Z- 20 2000 7.10 ethyl hexanoate). Pentaerythritol tetrap,p-Dloctyldiphenylamine 3 N one 39. 27 0. 06 (75/25 pelargonate/2- 300 5. 83 ethyl hexanoate). 3 Pentaerythritol tetra- None Potassium salt of naph- 0. 9 0 41. 0 0.30 (75/25 pelargonate/Z- thenic acid product of 0. 9 0. 1-K 20 1900 6. 22 ethyl hexanoate) average molecular wt. of 310 and Acid No. of

169 (Sunaptic Acid A).

70 Pentaerythritol tetrap,p-Dioctyldiphenylamine 3 Potassium salt of naph- 0. 9 0. 1K 0 41. 54 0. 33 (75/25 pelargonate/2- thenic acid product of 140 63, 94 0 50 ethyl hexauoate). average molecular wt.

of 310 and Acid No. of 169 (Sunaptic Acid A). I

71. Pentaerythritol tetrap,p-Dioctyldiphenylamlne 2. 5 Potassium salt of naph- 0, 9 0, 1-K Y 0 39, 79 0. 31 (75/25 pelargonate/2- Octylated styrenated 0.5 thenic acid product of -140 65. 77 0. 27 ethyl hexanoate). diphenylamine product. average molecular wt.

- of 310 and Acid No. of

169 (Sunaptic Acid A).

72 Pentaerythritol tetrap,p-Dioctyldiphenylamine 2. 5 Potassium salt of naph- 0.9 0.1'-K 0 :46 031' (75/25 pelargonate/Z- 5-ethyl-10,10-diphenyl- 0. 5 theme acid product of 140 63. 93 0:44 ethyl hexanoate). phenazasiline. average molecular wt.

310 and Acid No. of V H w v 169 (Sunaptic Acid A).

73 Pentaerythritol tetra- N-ethyl-p,p-dioctyldl- 2 Potassium salt of imide- 1 0.04K 0 88. 97 0. 05 (75/25 pelargonate/2- phenylamine. amide reaction product 40 85. 89 1. 21 ethylhexanoate). of Acid N o. 49 and derived trom EDTA and 01243 5 t-alkyl primary amine mixture reacted on 1:3 mole ratio basis.

74 Pentaerythritol tetra- Octylated styrenated v 5 Potassium salt of naph- 2. 5 0.28K 0 41, 60 0 05 (/50 octanoate/ diphenylamine product. them'c acid product of 80 67. 98 0 54 pelargonate). average molecular wt.

of 310 and Acid No. of 169 (Sunaptic Acid A).

75 Pentaerythritol tetrap,p-Dioctyldiphenylamine 3 Potassium salt of naph- 0. 9 0.01K 0 48. 0. 06 (50/50 pelargonate/ theme acid product of 120 79. 14 0. 35 2,2,-dimethyl average molecular wt. octanoate). of 310 and Acid No. of

169 (sunaptic Acid A). 76 Trimethylolpropane p,p-Dioctyldiphenylamine 3 Potassium salt of naph- 0.44 0,05-K-.. 0 31. 41 0 15 trlpelargonate. thenic acid product of 54. 32 0 47 average molecular wt. of 310 and Acid N o. of 169 (Sunaptic Acid A),

. 1 In percent by weight of ester oil portion.

portion and alkali metal salt portion of the composition of this invention function synergistically, that is to say, the antioxidant activity of the combination of the arylamine antioxidant portion and alkali metal salt portion is substantially greater than \the mere addition of the antioxidant activity of the arylamine antioxidant portions alone and the antioxidant activity of the alkali metal salt portion alone. Further evidence of this synergistic efiect is presented in connection with the following examples.

5 these specific embodiments.

Examples 77-78 These examples illustrate two more, specific embodiments of the lubricant oil composition of this invention.

These specific embodiments are made by admixing the components at 50-.90 C.

Table IX also sets forth typical data obtained actual- 1y subjecting to an oxidative stability test samples of these specific embodiments and ofv other compositions formulated as indicated in the table. The oxidative stability test employed in the Modified 425 tion Test.

for in Table IX is described F. AF- Oxida- TABLE IX Ester Oil Portion Arylamine Antioxidant Portion Alkali Metal Salt Portion Modified 500 13. AF

Oxidation Test Results Ex. Con- Con- Equiv- Oxida- Viscos- No. cencenalent tion ity in Acid Components Components tra- Components traalkali time centi- No.

tion 1 tion 1 metal in stokes at concenhours 100 F. tration 1 2-butyl-2-ethyl1,3pro- Octyl'ated styrenated di- 1. 5 None 14. 46 0. O1

panediol dipelarphenylamine product. 20 71. 68 10. 96 gunate.

2-butyl-2-ethyl-L3-pr'o- None Potassium salt of lmide- 1. 5 0 (lo-11- 0 14. 60 0.30 panediol dipelaramide reaction rroduct 26. 39 3. gonate. of Acid No. 49 and derived from EDTA and C C 5 t-alkyl primary amine mixture reacted on 1:3 mole ratio basis. 77. 2-butyl-2-ethyl-l,3-pro- Octylated styrenated di- 1. 0 Potassium salt of imide- 0.5 0.02-K. 0 14. 65 0. 03

, panediol dipelarphenylamine product. amide reaction product 20 15.32 0. M

gonate. of Acid No. 49 and de- 120 18.09 0. 23

rived from EDTA and C rC15 t-alkyl primary amine mixture reacted on 1:3 mole ratio basis. Trimethylopropane N-phenyl-l-naphthylamine- 1. 03 N 0 15. 48 0. 02 trlheptanoate. 5-ethyl-l0,l0-diphenyl 1.03 40 41. 52 7. 66

phenazasiline. Trimethylolpropane None Sodium salt of neotri- 2. 05 0.2Na 0 15. 48 0. 04 tn'heptanoate. decanoicacid. 40 19. 00 0.70 78 'Irimethylolpropane N-phenyl-l-naphthylamine 1. 0 Sodium salt of neotri- 0. 06 0.006Na 0 15. 73 0. 02 triheptanoate. 5-ethyl-10,10diphenyl- 1. 0 decanoic acid. 40 17. 07 0.97

phenazasiline.

1 In percent by weight of ester oil portion.

Not only do alkali metal salts of this invention activate arylamine antioxidants at temperatures of 425500 F., but they also appear to activate the activity of arylamine antioxidants at lower temperatures. This is demonstrated by some actual test data obtained inrunning a variation of the well known 347 F. oxidation test described in Method 5308.4, of Federal Test Method Standard No. 791, which test is employed to evaluate jet lubes for Military Specification 7808D. In this variation, a 25 milliliter sample of the lubricant under test is heated in a 25 millimeter x 350 millimeter Pyrex tube topped with a water condenser. The temperature of the lubricant sample is established and maintained at 347 F. while 1.25 liters of air per hour are blown through the sample. Metal washers inch diameter) of iron, copper, aluminum, magnesium and silver are disposed in. the sample on the air delivery tube. Periodically, the acid number of the sample is determined. When the acid number has increased by 2.0, the period ot time required to reach this condition is determined. This is referred to as the induction period or stable life of the lubricant. When this test was run on a sample of 2 'butyl-2-ethyl-1,3- propanediol dipelargonate containing N phenyl-I-naphthylamine at a concentration of 1% by weight of the ester, the induction period was 265 hours. When the test was run on another sample of the 2-butyl-2-ethyl-1,3- propane'diol dipelargonate containing not only N-phenyl- 1' naphthylamine at a concentration of 1% by weight of the ester, but also the potassium salt of an imide-amide reaction product of Acid No. 49 and derived from EDTA Examples 79-80 These examples illustrate still more specific embodiments of the lubricant oil composition of this invention.

tially of 2-butyl 2 ethyl-1,3-propanediol dipelargonate. The arylamine antioxidant portion consists essentially of N-phenyl 1 naphthylamine at a concentration of 1%- by weight of the ester oil portion and 5-ethyl-10,10-diphenylphenazasiline at a concentration of 1% by weight of the ester oil portion. The composition of the alkali metal salt portion is set forth in the following Table X.

These embodiments are made by admixing the components thereof at 50-90 C.

7 Table X also contains typical data obtained in testing for oxidative stability samples of these embodiments, of

the ester oil portion alone and of the ester oi-l portion with the arylamine antioxidant portion plus the metal salts indicated in Table X. The test employed is the 425 F. AF Oxidation Test.

The ester oil portion of these examples consists essen- TAB LE X Alkali Metal Salt Portion 425 F. AF Oxidation Test Results Example No. Concentration, Equivalent metal Viscosity in Component (s) percent by wt. concentration, Oxidation centistokes Acid N o.

of ester oil percent by wt. of time in hours at 100 F.

portion ester oil portion None 14. 88 0.03 40 59. 40 7. 50 79 Sodium stearate 0. 12s 0.0l-Na 0 14. 99 0. 0a 120 19. 53 0.87 80 Potassium stearate 0. 08 0.01K 0 14. 93 0. 04 120 17.50 0.54 Magnesium stearate 0. 24 0.01-Mg 0 15. 0. 04 40 40. 98 7. 16 Calcium stearate 0. 0.,01-Ca 0 15. 00 0. 04 40 53. 07 8. 32 Barium stearate 0. 05 0.01-Ba 0 14. 91 0.04 40 69. 59 8. 92 Barium stearate 0.10 0.02Ba 0 14. 97 0. 03 42. 75 8. Beryllium stearate 0.61 0.01-Be t. 0 15.21 0.04 65. 96 10. 06 Aluminum steal-ate 0. 36 0.01-Al 0 15. 11 0.03 40 96. 73 6. 84 Cadmium stearate 0. 07 0.01-Cd 0 14. 96 0. 03 40 67.73 8.73 Zinc stearate 0. 11 0.01-Zn 0 15. 03 0. 04 40 33. 95 7. 29 Vanadium stearate o. 19 col-V. 0 15. 02 o. 04 20 161. 62 14. 53 Iron stearate "1."- 0. l8 0.01-Fe. 0 15.02 0.04 20 119.04 10.73 Nickle stearate 0. 12 0.01-Ni 0 15. 01 0. 03 40 46.84 6 22 These data of Table X show that of the metal salts of stearic acid only the alkali metal salts of stearate acid appear to activate arylamine antioxidants at temperatures above 300 F. Hence, the alkali metal salts of the invention generally appear to occupy a unique position relative to arylamine antioxidants generally when employed in synthetic ester oil.

Other features, advantages and specific embodiments of this invention will occur to those in the exercise of ordinary skill in the art after reading the foregoing disclosures. In this connection, while specific embodiments ofthis invention have been described in considerable detail, variation and modifications of them can be effected without departing from the spirit and scope of the inven tion as disclosed and claimed.

We claim:

1. A normally liquid composition useful as a lubricant which consists essentially of (a) a synthetic ester oil portion and (b) at a protective concentration a mixture consisting essentially of (1) an arylamine antioxidant portion consisting essentially of an arylamine selected from the group consisting of diphenylamines, N-phenylnaphthylamines, dinaphthylamines, phenothiazines, phenylenediamines and diphenylphenazasilines and (2) an alkali metal salt ortion consisting essentially of at least one alkali metal salt selected from the group consisting of alkali metal salts of hydrocarbon carboxylic acids, alkali metal salts of an imide-amide reaction product of a hydrocarbon aminocarboxylic acid and an alkyl amine, alkali metal salts of carboxy terminated polyesters and alkali metal salts of hydroxy aromatic compounds selected from the group consisting of naphthols and hydroxyanthraquinones, the concentration of the alkali metal salt portion being such that the alkali metal concentration is in a range from about 0.001 to about 0.5% by weight of said synthetic ester oil portion and the weight ratio of alkali metal to said arylamine antioxidant is in a range from about 1:30 to about 1:1000.

2. A normally liquid composition useful as a lubricant, which consists essentially of (a) a synthetic ester oil portion and (b) at a concentration in a range from about 0.2 to above 10% by Weight of said synthetic ester oil portion a mixture consisting essentially (1) an arylamine antioxidant portion consisting essentially of an arylamine selected from the group consisting of diphenylamines, N-phenylnaphthylamines, dinaphthylamines, phenothiazines, phenylenediamines and diphenylphenazasilines and (2) an alkali metal salt portion consisting essentially of at least one alkali metal salt selected from the group consisting of alkali metal salts of hydrocarbon carboxylic acids, alkali metal salts of an imide-amide reaction product of a hydrocarbon aminocarboxylic acid and an alkylamine, alkali metal salts of carboxy terminated polyesters and alkali metal salts of hydroxy aromatic compounds selected from the group consisting of naphthols and hydroxyanthraquinones, the concentration of the alkali metal salt portion being such that the alkali metal concentration is in the range from about 0.001 to about 0.5% by weight of said synthetic ester oil portion and the weight ratio of alkali metal to said arylamine antioxidant portion is in a range from about 1:30 to about 1:1000.

3. A normally liquid composition useful as a lubricant, Which consists essentially of (a) a synthetic ester oil portion consisting essentially of at least one normally liquid, synthetic ester and (b) at a concentration in a range from about 0.5 to about 5% by weight of said synthetic ester oil portion a mixture 21 consisting essentially of 1) an arylamine antioxidant portion consisting essentially of at least one arylamine antioxidant selected from the group consisting of diphenylamines, N-phenylnaphthlamines, dinaphthylamines, phenothiazines, phenylenediamines and di-phenylphenazasilines and (2) an alkali metal salt portion consisting essentially of at least one alkali metal salt selected from the group consisting of alkali metal salts of hydrocarbon carboxylic acids, alkali metal salts of the imide-amide reaction products of a hydrocarbon aminocarboxylic acid and an alkylamine, alkali metal salts of carboxy terminated polyesters and alkali metal salts of hydroxy aromatic compounds selected from the group consisting of naphthols and hy-droxyanthraquinones, the concentration of said alkali metal salt portion being such that the alkali metal concentration is in a range from about 0.005 to about 0.5% by weight of said synthetic ester oil portion and the weight ratio of alkali metal to said arylamine antioxidant portion is in a range from about 1:30 to about 1:1000.

4. A normally liquid composition useful as a lubricant, which consists essentially of (a) a synthetic ester oil portion consisting essentially of 2-butyl-'2-ethyl-l,3- propanediol dipelargonate and (b) at a concentration in a range from about 0.5 to about by weight of said synthetic ester oil portion a mixture consisting essentially of (1) an arylamine antioxidant portion consisting essentially of at least one arylamine antioxidant selected from the group consisting of diphenylamines, N-phenylnaphthylamines, dinaphthylamines, phenothiazines, phenylenediamines and diphenylphenazasilines and (2) an alkali metal salt portion consisting essentially of at least one alkali metal salt selected from the group consisting of alkali metal salts of hydrocarbon carboxylic acids, alkali metal salts of the imide-amide reaction product of a hydrocarbon aminocarboxylic acid and an alkylamine, alkali metal salts of carboxy terminated polyesters and alkali metal salts of hydroxy aromatic compounds selected from the group consisting of naphthols and hydroxyanthraquinones, the concentration of said alkali metal salt portion being such that the alkali metal concentration is in a range from about 0.005 to about 0.5% by weight of said synthetic ester oil portion and the weight ratio of alkali metal to said arylamine antioxidant portion is in a range from about 1:30 to about 1:1000.

5. A composition according to claim 4 wherein said arylamine antioxidant portion consists essentially of N- phenyl-l-naphthylamine and 5-ethyl-10,l0-diphenylphenazasiline.

6. A composition according to claim 5 wherein said alkali metal salt portion consists essentially of an alkali metal salt of an imide-amide reaction product made by cooking at a temperature of 190-220 C. until an acid number in a range from about to about 150 is obtained a mixture consisting essentially of at least one hydrocarbon aminocarboxylic acid and at least one C -C aliphatic primary amine at a mole ratio of acid to amine in the range from about 1:2 to about 1:4, whereby an imideamide reaction product is formed and then neutralizing the reaction product to at least 90% of its acidity with at least one alkali metal hydroxide.

7. A composition according to claim 6 wherein said aminocarboxylic acid is ethylenediamine tctraacetic acid and said alkali metal hydroxide is potassium hydroxide.

8. A composition according to claim 4 wherein said arylamine antioxidant portion is selected from the group consisting of an octyldiphenylamine or an octylated styrenated diphenylamine product.

9. A composition according to claim 8 wherein said alkali metal salt portion consists of at least one alkali metal salt of a naphthenic acid.

10. A normally liquid composition useful as a lubricant which consists essentially of (a) a synthetic ester oil portion consisting essentially of trimethylolpropane triheptanoate and (b) at a concentration in a range from about 0.5 to about 5% by weight of said synthetic ester oil portion a mixture consisting essentially of (1) an arylamine antioxidant portion consisting essentially of at least one arylamine antioxidant selected from the group consisting of diphenylamines, N-phenylnaphthylamines, dinaphthylamines, phenothiazines, phenylenediamines and diphenylphenazasilines and (2) an alkali metal salt portion consisting essentially of at least one alkali metal salt selected from the group consisting of alkali metal salts of hydrocarbon carboxylic acids, alkali metal salts of the imide-amide reaction product of a hydrocarbon aminocarboxylic acid and an alkylamine, alkali metal salts of carboxy terminated polyesters and alkali metal salts of hydroxy aromatic compounds selected from the group consisting of naphthols and hydroxyanthraquinones, the concentration of said alkali metal salt portion being such that the alkali metal concentration is in a range from about 0.005 to about 0.5% by weight of said synthetic ester oil portion and the weight ratio of alkali metal to said arylamine antioxidant portion is in a range from about 1:30 to about 1:1000.

11. A composition according to claim 10 wherein said arylamine antioxidant portion consists essentially of N-phenyl-l-naphthylamine and 5-ethyl-10,10-diphenylphenazasiline.

12. A composition according to claim 11 wherein said alkali metal salt portion consists essentially of the sodium salt of neotridecanoic acid.

13. A normally liquid composition useful as a lubricant, which consists essentially of (a) a synthetic ester oil portion consisting essentially of pentaerythritol tetra- (mixed pelargonate/Z-ethylhexanoate) and (b) a concentration in the range from about 0.5 to about 5% by weight of said synthetic ester oil portion a mixture consisting essentially of (1) an arylamine antioxidant portion consisting essentially of at least one arylamine antioxidant selected from the group consisting of diphenylamines, N- phenylnaphthylamines, dinaphthylamines, phenothiazines, phenylenediarnines and diphenylphenazasilines and (2) an alkali metal salt portion selected from the group consisting of alkali metal salts of hydrocarbon carboxylic acids, alkali metal salts of the imide-amide reaction product of a hydrocarbon aminocarboxylic acid and an alkyl amine, alkali metal salts of carboxy terminated polyesters and alkali metal salts of hydroxy aromatic compounds selected from the group consisting of naphthols and hydroxyanthraquinones, the concentration of said alkali metal salt portion being such that the alkali metal concentration is in a range from about 0.005 to about 0.5% by weight of said synthetic ester oil portion and the weight ratio of alkali metal to said arylamine antioxidant portion is in a general range from about 1:30 to l: 1000.

14. A composition according to claim 13 wherein said arylamine antioxidant portion consists essentially of p,p'- dioctyldiphenylamine.

15. A composition according to claim 14 wherein said alkali metal salt consists essentially of at least one alkali metal salt of a naphthenic acid.

16. An antioxidant composition useful for synthetic ester lubricants, which comprises a mixture consisting essentially of (1) an arylamine antioxidant portion consisting essentially of at least one arylamine antioxidant selected from the group consisting of diphenylamines, N-phenylnaphthylamines, dinaphthylamines, phenothiazines, phenylenediamines, and diphenylphenazasilines and (2) as a high temperature activator for said arylamine antioxidant portion an alkali metal salt portion consisting essentially of at least one alkali metal salt selected from the group consisting of alkali metal salts of hydrocarbon carboxylic acids, alkali metal salts of the imide-amide reaction product of a hydrocarbon aminocarboxylic acid and an alkyl amine, alkali metal salts of carboxy termi nated polyesters and alkali metal salts of hydroxy aromatic compounds selected from the group consisting of naphthols and hydroxyanthraquinones, the concentration of said alkali metal salt portion being such that the weight ratio of alkali metal to said arylamine antioxidant portion is in a range from about 1:30 to about 1:1000.

17. A composition according to claim 16 wherein said arylamine antioxidant is a diphenylamine selected from the group consisting of diphenylamine, p-octyldiphenylamine or p,p'-dioctyldiphenylamine.

18. A composition according to claim 16 wherein said arylamine antioxidant portion includes 5-ethyl-10,lO-diphenylphenazasiline.

19. A composition according to claim 16 wherein said arylamine antioxidant in said arylamine portion is selected from the group consisting of an octylated diphenylamine product or an octylated styrenated diphenylamine product.

20. A composition according to claim 16 wherein said arylamine antioxidant is a dinaphthylamine selected from the group consisting of dinaphthylamine or di-Z-naphthylamine.

21. A composition according to claim 16 wherein said arylamine antioxidant is a phenothiazine selected from the group consisting of phenothiazine or N-ethylphenothiazlne.

22. A composition according to claim 16 wherein said alkali metal salt portion consists essentially of at least one alkali metal salt of a hydrocarbon carboxylic acid selected from the group consisting of a naphthenic acid or an aliphatic carboxylic acid having 1 to 18 carbon atoms.

23. A composition according to claim 16 wherein said alkali metal salt portion consists essentially of at least one alkali metal salt of an imide-arnide reaction product made by cooking at a temperature of 190220 C. until an Acid No. in the range from about to about 150 is obtained a mixture consisting essentially of at least one hydrocarbon aminocarboxylic acid and at least one C C aliphatic primary amine at a mole ratio of acid to amine in the range from about 1:2 to about 1:4, whereby an imide-amide reaction product is formed, and neutralizing said reaction product to at least 90% of its acidity With at least one alkali metal hydroxide.

24. An antioxidant composition useful in synthetic ester lubricants which comprises a mixture consisting essentially of (1) an arylamine antioxidant portion consisting essentially of at least one arylamine antioxidant selected from the group consisting of diphenylamines, N-phenylnaphthylamines, dinaphthylamines, phenothiazines, phenylenediamines, and diphenylphenazasilines and (2) as a high temperature activator for said arylamine antioxidant portion an alkali metal salt of an imideamide reaction product made by cooking at a temperature of l90'220 C. until an Acid No. in a range from about 10 to about 150 is obtained a mixture consisting essentially of at least one hydrocarbon aminocarboxylic acid and at least one C -C aliphatic primary amine at a mole ratio of acid to amine in the range from about 1:2 to about 1:4, whereby an imide-amide reaction product is formed and neutralizing said reaction product to at least of its acidity with at least one alkali metal hydroxide.

25. An antioxidant composition useful in synthetic ester lubricants which comprises the mixture consisting essentially of (1) an arylamine antioxidant portion consisting essentially of N-phenyl-l-naphthylamine and 5- ethyl-10,IO-diphenylphenazasiline and (2) as a high temperature activator for said arylamine antioxidant portion an alkali metal salt of an imide-amide reaction product made by cooking at a temperature of 190-220 C. until an acid number in a range from about 10 to about is obtained a mixture consisting essentially of at least one hydrocarbon aminocarboxylic acid and at least one C -C aliphatic primary amine at a mole ratio of acid to amine in the range from about 1:2 to about 1:4, whereby an imide-amide reaction product is formed and neutralizing said reaction product to at least 90% of its acidity with at least one alkali metal hydroxide.

References Cited UNITED STATES PATENTS 2,001,108 5/ 1935 Parker 252-39 X 2,079,051 5/1937 Sullivan et al 25218 2,321,577 6/1943 Clayton et a1 252-49.7 X 2,344,988 3/1944 Kavanagh et al 25242.7 2,954,342 '9/1960 Hotten 25242.1 X 3,053,768 9/19 62 Cupper 252-56 X 3,115,519 12/1963 Crouse et a1 25256 X 3,126,344 3/ 1964 Matuszak et al 25256 X OTHER REFERENCES Barnes et al., Synthetic Ester Lubricants, Petroleum Engineering, August 1957, pp. 454-458.

DANIEL E. WYMAN, Primary Examiner. P. P. GARVIN, Assistant Examiner. 

1. A NORMALLY LIQUID COMPOSITION USEFUL AS A LUBRICANT WHICH CONSISTS ESSENTIALLY OF (A) A SYNTHETIC ESTER OIL PORTION AND (B) AT A PROTECTIVE CONCENTRATION A MIXTURE CONSISTING ESSENTIALLY OF (1) AN ARYLAMINE ANTIOXIDANT PORTION CONSISTING ESSENTIALLY OF ARYLAMINE SELECTED FROM THE GROUP CONSISTING OF DIPHENYLAMINES, N-PHENYLNAPHTHYLAMINES, DINAPHTHYLAMINES, PHENOTHIAZINES, PHENYLENEDIAMINES AND DIPHENYLPHENAZASILINES AND (2) AN ALKALI METAL SALT PORTION CONSISTING ESSENTAILLY OF AT LEAST ONE ALKALI METAL SALT SELECTED FROM THE GROUP CONSISTING OF ALKALI METAL SALTS OF HYDROCARBON CARBOXYLIC ACIDS, ALKALI METAL SALTS OF AN IMIDE-AMIDE REACTION PRODUCT OF A HYDROCARBON AMINOCARBOXYLIC ACID AND AN ALKYL AMINE, ALKALI METAL SALTS OF CARBOXY TERMINATED POLYESTERS AND ALKALI METAL SALTS OF HYDROXY AROMATIC CMPOUNDS SELECTED FROM THE GROUP CONSISTING OF NAPHTHOLS AND HYDROXYANTHRAQUINONES, THE CONCENTRATION OF THE ALKALI METAL SALT PORTION BEING SUCH THAT THE ALKALI METAL CONCENTRATION IS IN A RANGE FROM ABOUT 0.001 TO ABOUT 0.5% BY WEIGHT OF SAID SYNTHETIC ESTER OIL PORTION AND THE WEIGHT RATIO OF ALKALI METAL TO SAID ARYLAMINE ANTIOXIDANT IS IN A RANGE FRM ABOUT 1:30 TO ABOUT 1:1000. 